To get our bearings straight it is necessary at the outset to draw a clear distinction between these four terms: declaration of nullity, annulment, legal separation, and divorce.
Declaration of Nullity
One often meets people, even well-educated ones, who misconstrue a declaration of nullity as a decree of divorce. One often hears it said that moneyed people can bring their cases to Rome and obtain an ecclesiastical sentence allowing them to go their separate ways and remarry. And if this is not divorce, then what is it?
The answer is, what these people get is not a divorce decree but a declaration of nullity, which is an altogether different case.
Marriage, it is true, is much more than a contract. It is a state of life. More than that, it is an interpersonal relationship. True, very true. But it is no less than true that the gateway to this interpersonal relationship and state of life is the marriage contract. By this contract a man and a woman acquire the right to the sort of interpersonal behavior and relations that are the woof and warp of the married state of life. Now, as in all contracts, certain conditions are required by law for the marriage contract to be valid or binding. The more important and fundamental the contract, the more it directly affects the parties to it, the more reasonable it is that the competent authority should set conditions and regulate it. This is exactly the case with the marriage contract because its subject-matter is the very bodies and persons of the contracting parties themselves.
Where any of the requisites for the validity of the contract is wanting, then the contract is null and void from the very beginning. In plain terms, there never was any contract at all.
Annulment
A declaration of nullity should never be confused with an annulment. Annulment is the voiding of a defective contract that is valid and binding from the beginning up to the moment of its annulment. When a marriage is annulled, there was a valid marriage and the couple was truly man and wife up to the time when the sentence of annulment takes effect. On the other hand, in a declaration of nullity there never was a valid and binding contract. When a marriage is declared null and void there is no unmaking of what was made and existed before. There is only an official finding that there never was a marriage, that the couple was never truly man and wife, because some essential requisite or requisites for validity were wanting at the time the marriage contract was solemnized.
What happened in this case is that the couple mistakenly thought they had contracted a valid marriage, whereas in truth a defective marriage had taken place and they never were man and wife. When the error is detected, the couple either contracts a valid marriage, i.e., makes good the defective contract in any of the ways provided by law, or else they are bound to separate. If they choose the latter alternative, since they never were married, it is plain that both are free to marry someone else.
It must always be kept in mind that a declaration of nullity does not dissolve or unmake a marriage simply because there is no marriage to dissolve or unmake. On the other hand, annulment, legal separation, divorce, always imply or presuppose a valid marriage contract and valid marriage bond, binding the man and the woman together in the state of matrimony.
Legal Separation
A valid marriage produces two effects. In the first place, each party gives to the other the exclusive right to his/her body for the performance of the marital act. In the second place, a natural corollary of the right to the marital act, the marriage contract effects a certain unity of life whereby the man and the woman share the same roof, board, and bed.
When a married couple are allowed by judicial sentence to break this complementary unity of life---i.e., when they no longer sleep together nor live in the same house--- we have an imperfect or relative divorce, more commonly and better known as legal separation.
Divorce
It should be obvious that what binds people in the state of matrimony is neither geographical nor physical togetherness. It is the marital rights and duties exchanges by the marriage contract. So long as these rights and duties subsist, the man is bound to the woman and the woman is bound to the man even if they should no longer live together. And so long as the bond subsists, the marriage subsists.
When the man and the wife agree not merely to sleep in different rooms, or live in different houses, but take the further step of revoking the exclusive rights they mutually gave each other, then the marriage bond itself is broken, the marriage is dissolved. This is what is meant by divorce, in the proper or absolute sense of the term.
Employed without qualifications, this term always stand for perfect or absolute divorce. (It is better, in order to preclude misunderstanding, to designate the imperfect or relative divorce by the term legal separation.) Proponents of divorce are fundamentally interested in the right to remarry. This right to remarry is absent in mere legal separation where, despite the separation of bed, board, and roof, the parties remain bound or married to each other, and therefore precluded from entering into another marriage. It is precisely the dissolution of the marriage bond which absolute divorce effects, that leaves the divorced parties free to marry again.
The Catholic Position
The Church officially admits the declaration of nullity, annulment, and legal separation. With respect to the latter the Church usually grants legal separation on broader grounds than the civil code. For instance, the present Philippine Civil Code provides for only three causes for legal separation, viz., adultery on the wife's part, concubinage on the husband's part, and attempt by either spouse on the life of the other. On the other hand, Canon Law provides for other additional causes, e.g., criminal and ignominious life of the other spouse, cruelty. Furthermore, legal separation is ordinarily effected by order of the competent authority; however, the Canon Law allows the innocent party to leave the guilty one on his or her authority if there be a danger in delay.
Annulment of Non-consummated Marriage
Likewise Canon Law admits the annulment of marriage. This is granted for cause, usually in the case of a validly contracted but not consummated marriage. When a valid contract is voided the contracting parties are returned to the status they had prior to the contract, as if the contract had not taken place. In the case of marriage this is possible before the marriage is consummated, but it is plain impossible after its consummation.
Furthermore, marriage is not a run-of-the-mill contract. It is an exceptionally exceptional contract, unique, because its subject-matter is the very persons of the contracting parties and it has the profoundest repercussions in their intimate personal lives. Marriage is a total giving of the self to another. If liberty is an essential ingredient of any contract, it stands to any reason that utmost liberty ought to be available and guaranteeable for this exceptionally exceptional contract. The point of no return where freedom must make its choice is the definitive ratification of the marriage contract represented by the actual taking and possessing of each other's person in the marital act which is the consummation of the contract.
Conversely, here is the last rampart and defense of the individual's liberty. Often a man or a woman is compelled to go through a skillfully camouflaged shotgun marriage. Is the wedding ceremony the moment of truth? Of course not. After the ceremony is ended and the documents are duly signed and witnessed, after the reception is through and the guests have gone home, the moment of truth comes in the privacy of the nuptial chamber and bed. Duress can disguised and dissimulated so that none of the guests and witnesses is any wiser. But in the sanctuary of the nuptial chamber consummation ordinarily does not take place without the free volition of both parties. The moment of truth arrives. Consummation is strong evidence, albeit in some cases not proof, that the parties have changed their minds and now, under no compulsion, freely ratify the contract and take each other as man and wife in the marital act. On the contrary, a persistent refusal of consummation is the strongest proof of a continuing repudiation of the marriage celebrated under duress. Thus, consummation or non-consummation is humanly the clearest available indicator of free consent, or lack of it, to the marriage contract.
Thus, the point at issue boils down to divorce, i.e., to the dissolution of the marriage bond and the consequent freedom to remarry in the case of a validly contracted and consummated marriage.
